[3.12] gh-131670: Fix crash in `anext()` when `__anext__` is sync and raises (GH-131682) (#131687)

gh-131670: Fix crash in `anext()` when `__anext__` is sync and raises (GH-131682)
(cherry picked from commit 929afd1d6ee4fb89ac818037effe6577947103de)

Co-authored-by: sobolevn <mail@sobolevn.me>
Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>